1. Field of the Invention
The present invention relates to an ink jet printing apparatus and an ink jet printing method, and more particularly to a “marginless printing” (or a full-bleed printing) which prints an image edge to edge on a print medium of irregular shape that has undulations or inclined or curved edges in peripheral portions and holes of arbitrary shape in an intenor portion.
2. Description of the Related Art
Ink jet printing apparatus have seen rapid reductions in price and size in recent years and an increasing number of them are entering the market for personal use. There are growing demands on these ink jet printing apparatus for a variety of multiple functions in addition to improved image quality and faster printing speed, and useful functions for users are being realized one after another. For example, a printing construction for a so-called “marginless printing” that prints on a print medium edge to edge without a margin has become available.
In printing on a print medium edge to edge, to realize a secure, reliable “marginless printing” requires ejecting some volume of ink onto areas overrunning outwardly from the edges of the print medium. Thus, conventional ink jet printing apparatus must overcome important technical problems, i.e., it is necessary to minimize those printed areas overrunning from the edges of the print medium and a volume of ink applied to the overrunning areas and to prevent, as practically as possible, an interior of the printing apparatus from being contaminated by the ink applied to the overrunning areas. A few printing methods and constructions to solve these problems have been proposed, for instance, in Japanese Patent Application Laid-open No. 2000-351205. Also a number of printing apparatus employing these methods and constructions are currently available.
To minimize the size of the overrunning area and the amount of ink applied to the overrunning area during the “marginless printing,” it is desired that the position of the edges of a print medium be determined as correctly as possible. In the conventional construction, since the print medium is assumed to have a rectangular shape and a regular size, such as A4 size or post card size, it is possible to recognize the front and rear edge positions and lateral edge positions of the print medium with a relatively simple means. That is, if the user sets a paper size on a printer driver screen and if a print medium is fed into the printing apparatus with one of the lateral ends of the print medium fixed and the front edge of the print medium is detected by some means, it is possible to determine the front and rear edge positions and the left and right edge positions of the print medium.
Now, the printing method as performed during the “marginless printing” in a conventional ink jet printing apparatus will be briefly described.
FIG. 1 is a perspective view showing how a “marginless printing” is performed on A4-size paper. In the figure, denoted 1 is a print head which is positioned and held on a carriage not shown and can be moved in a main scan direction indicated by an arrow B as it is guided along a guide shaft and a rail The print head 1 is provided with nozzles 1A of a black ink and nozzles 1B of color inks.
Designated 2 is a platen for holding a print medium 100. The platen 2 has a notched portion or overrunning ink reception opening 3 that receives ink applied outside the edge of the print medium 100 during the “marginless printing”. The overrunning ink reception opening 3 extends in a direction of arrow B in which the print head 1 travels, so that it can receive ink droplets ejected from the print head 1 wherever the print head may be. It is noted that the overrunning ink reception opening 3 has widened portions 3A-3F extending in the print medium transport direction at positions corresponding to widthwise edges of different sizes of the print medium. In the figure, 3A represents a portion corresponding to the left edge of a print medium that constitutes a reference, 3C represents a portion corresponding to the right edge of a post card with its left edge aligned with the reference, 3B represents a portion corresponding to the right edge of an L-size photograph, 3D represents a portion corresponding to the right edge of a 2L-size photograph, 3E represents a portion corresponding to the right edge of a “4×6-inch”size, and 3F represents a portion corresponding to the right edge of A4-size and LTR-size. The figure shows an A4-size print medium 100 as an example.
FIG. 1 shows a state in which the print medium 100 is fed and a “marginless printing” by the print head 1 is about to start at a front edge portion 100A of the print medium. At this time the front edge portion 100A is situated directly above the overrunning ink reception opening 3 and the left and right edges directly above 3A and 3F. Ink droplets applied to a U-shaped area overrunning from the edge of the print medium 100 are all accommodated in the overrunning ink reception opening 3. With the print medium 100 positioned in this state, the print head 1 starts the marginless printing on the front edge portion 100A of the print medium as it moves in the main scan direction (arrow B direction).
The print head 1 has a nozzle column 1A for ejecting a black ink and nozzle columns 1B for ejecting a plurality of color inks Each of the nozzle columns has a plurality of nozzles arranged in a direction of arrow A at a predetermined pitch over a width D. When the front edge portion 100A of the print medium 100 is printed, not all nozzles in each nozzle column of each color are activated over the width D. As shown in the figure, only those nozzles that correspond to a particular width near the center, like a width C (<D) in the figure, are used for printing. By adopting this printing method, the ink droplets applied outside the front edge portion 100A can be securely accommodated in the overrunning ink reception opening 3. Further, by not setting the overrunning ink reception opening 3 unnecessarily large, a stability with which the platen 2 supports the print medium 100 can be prevented from deteriorating as practically as possible The front edge portion 100A is printed by alternately repeating the printing scan using the nozzle column width range C and the operation of feeding the print medium a corresponding distance. When, after the printing operation has proceeded, the front edge portion 100A well exceeds the nozzle column width range D, the printing on the front edge portion 100A is completed.
FIG. 2 is a perspective view showing a state in which the front edge portion 100A of the print medium 100 is completed and the “marginless printing” is being performed on a normal portion of the print medium. In the normal portion a full column width range D of the nozzle columns in the print head 1 is used. At positions on the platen 2 corresponding to a left edge portion 100B and a right edge portion 100C of the print medium 100 there are provided overrunning ink reception openings 3A and 3F which extend over a distance J, longer than the width D. Ink droplets applied outside the left and right edges of the print medium are reliably accommodated in the overrunning ink reception openings 3A and 3F. By repetitively alternating the printing scan using the column width range D in the print head and the print medium feeding over a corresponding distance, the printing on the normal portion is performed. When, after the printing has proceeded, a rear edge portion 100D approaches the column width range D in the print head, the printing on the normal portion is completed and transferred to the printing on the rear edge portion 100D.
FIG. 3 is a perspective view showing a state in which the printing on the normal portion is completed and a “marginless printing” is being performed on the rear edge portion 100D of the print medium 100. In the printing on the rear edge portion, the range C of the nozzle columns is activated as in the printing of the front edge portion. The rear edge portion l00D is situated directly above the overrunning ink reception opening 3 and the left and right edges are situated directly above 3A and 3F, so that ink droplets applied to a U-shaped area overrunning from the edge of the print medium 100 are all accommodated in the overrunning ink reception opening 3. When the printing on all the area of the print medium is complete, the print medium 100 is transported in the direction of arrow A by a transport means (not shown) and discharged.
FIG. 4 is a perspective view showing a state in which a “marginless printing” is being performed on a print medium 100 of photograph 2L-size. As described above, 3B-3F represent portions of the overrunning ink reception opening 3 having an increased width that are provided for different sizes of print medium. In the case of photograph 2L-size, its left edge portion and right edge portion are situated at positions 3A and 3D respectively. As described above, in the conventional ink jet printing apparatus, the “marginless printing” can be performed on any available size of the print medium, as in the case of A4-size print medium explained in FIG. 1 to FIG. 3.
To cope with a variety of uses in recent years, irregular shapes of print mediums have been made available which have undulations or inclined or curved edges in peripheral portions and holes in an interior portion thereof. While there are growing demands on the ink jet printing apparatus for a construction capable of performing a satisfactory printing on such irregular-shaped print mediums and for a marginless printing capability, the conventional construction has difficulty fully meeting these demands, as described in the section of related art. That is, in the ink jet printing apparatus of the conventional construction, since the print medium is assumed to have a regular, rectangular shape, the positions of edges of the print medium can be determined relatively easily. With irregularly shaped print mediums, however, the edge positions are difficult to determine, which in turn renders a correct printing impossible or results in applying ink to an area excessively overrunning from the edges, contaminating the interior of the printing apparatus.